Site-Specific Channel Modeling and Optimization of RIS-Assisted Multiuser MISO Systems

TL;DR

This paper develops a physics-based, site-specific channel modeling and optimization framework for RIS-assisted multi-user MISO systems, combining ray-tracing and electromagnetic analysis to improve system design and deployment accuracy.

Contribution

It introduces a hybrid RT and electromagnetic analysis approach for deterministic channel modeling and an alternating optimization scheme for joint BS and RIS configuration in realistic environments.

Findings

Model accurately captures multipath, RIS scattering, and mutual coupling effects.

Optimization improves minimum achievable rate under practical constraints.

Simulation and measurement results show high agreement and practical relevance.

Abstract

This paper presents a physics-based channel modeling and optimization framework for reconfigurable intelligent surface (RIS)-assisted downlink multi-user multiple-input single-output (MU-MISO) communication systems in site-specific environments. A hybrid ray-tracing (RT) and full-wave electromagnetic analysis approach is developed to construct a deterministic channel model that explicitly captures multipath propagation, RIS scattering behavior, and mutual coupling effects through a non-diagonal load impedance representation. Based on this model, an alternating optimization scheme jointly updates the base-station (BS) beamformer and RIS load impedances to maximize the minimum achievable rate under a total transmit power constraint and practical capacitance limits. The objective of the proposed framework is to provide a reliable initial assessment of the system-level impact of RIS deployment in realistic propagation scenarios. To evaluate this capability, the RIS is operated in a column-paired 1-bit control mode that enables exhaustive evaluation of all realizable configurations in both simulation and measurement. Performance is compared at the distribution level through achievable-rate histograms across all configurations and further examined under small user-location variations. The observed agreement between simulation and measurement demonstrates that the proposed framework reliably captures practical performance trends and provides useful guidance for the design and deployment of RIS-assisted MU-MISO systems in site-specific environments.